1. Field of the Invention
The present invention relates to an apparatus and method of enhancing fluid and gas recovery from a well. In particular, the invention relates to enhancing oil and gas recovery from a well in an environmentally friendly manner.
2. Related Art
It is of some importance to discuss the background of the oil and gas recovery process in order to best appreciate the invention. An oil or gas pool requires a reservoir rock that is porous and permeable and a trap to contain the oil or gas. The oil or gas travels from its source into and through the reservoir rock to the trap.
The trap usually is an impermeable rock which encloses above the reservoir rock. Due to buoyancy and time, the less dense oil or gas migrates to the top of the trap, displaces the salt water, and remains in the trap. Thus, several layers form including gas at the top, then light oils, heavier oils, oil and saltwater mixtures and saltwater at the bottom.
Each well has inherent flow characteristics. The type of trap and geographical formation make up part of the natural flow characteristics of a pool of gas and oil. Common types of traps are dome, structural traps (created by relationships involving faults), and stratigraphic traps (resulting from variations in the layers, or strata).
Sedimentary rock usually forms reservoir rocks under certain conditions. Most reservoir rocks consist of sandstone or limestone due to their permeable and porous characteristics.
Most wells are drilled via a rotary bit method as is known in the art. When the drilling reaches oil-bearing formations the limits of the field are determined via formation samples and running well logs, a casing pipe is installed with production piping lowered into the casing which is used to withdraw the fluids through perforations in the casing.
Initially, the rate of the flow and the pressure and volume of the well are controlled by special pipings and gate valves--called a "Christmas tree"--installed above ground. Production begins when the optimal depth of the well is determined, at which point the pump is set to such depth to allow optimum exploitation of the well. The recovery of oil and gas requires the use of separation equipment. Natural gas must be separated from the liquid petroleum and salt water.
Initial production is usually through the mechanism of primary recovery, wherein the oil and gas field's own pressure drives the oil or gas to the surface. Over time, the pressure in the field drops. The oil must be pumped up to maintain production levels and difficulty resides in knowing what depth and for how long the pumping must be maintained for economic viability. A common drawback is that pumping the well causes removal of unwanted saltwater from the well because it has a tendency to mix with the oil and gas as it enters the perforations in the casing as the reservoir decreases. While some of the gas is utilized in conventional methods, a great deal of gas is wasted and placed into the atmosphere during the separation process due to their design as illustrated in FIG. 4.
Presently, about one-quarter to one-third of the oil is recovered through pumping, depending on the characteristics of the field. Natural gas recovery is usually much higher due to its natural properties of removal.
Expensive secondary and tertiary recovery methods are employed to increase recovery. Secondary recovery injects water or gas into the field to restore pressure and increase the proportion of petroleum removed from the field. Tertiary recovery injects steam, acids, carbon dioxide, detergents into the well to heat the oil, especially where it is "heavy" and flows poorly. These methods are not as desirable as primary methods.
It is desirable to employ less expensive recovery techniques while maximizing recovery in an environmentally acceptable manner. There exists a need for removing oil and gas from a reservoir in a manner such that the reservoir water substantially remains in the well. There is also a need to reduce waste of natural resources.